The present invention relates to a laser surveying instrument for projecting a laser beam in rotary irradiation and for forming a reference plane and a reference line. In particular, the present invention relates to a laser surveying instrument with waterproof function.
As a type of laser surveying instrument used for forming a reference plane and a reference line, which are required for operations of civil engineering work, building and construction project, etc. a laser surveying instrument for projecting a laser beam in rotary irradiation is known.
A laser surveying instrument has a rotating unit for deflecting and projecting a laser beam. By rotating the rotating unit, a reference plane or a reference line is formed by the laser beam.
The laser surveying instrument may be used under outdoor conditions, and the laser surveying instrument must have waterproof function so that the laser surveying instrument can also be used under rainy weather.
A laser surveying instrument with waterproof function has been known in the past, which has waterproof structure to enclose the rotating part by a cover with transparency. A type of laser surveying instrument having simple and inexpensive waterproof structure is disclosed in U.S. Pat. No. 6,643,004.
Referring to FIG. 6, description will be given below on a conventional type laser surveying instrument.
Inside a housing 1, a rotation mechanism accommodating unit 3 is movably supported in two directions perpendicularly crossing each other via a gimbal supporting unit 2. A rotation shaft 4 extending in a vertical direction is rotatably supported on the rotation mechanism accommodating unit 3. The rotation shaft 4 is connected with a motor 5, and an encoder 6 is mounted on the rotation shaft 4.
On the upper end of the rotation shaft 4, a rotary head 7 is mounted, and a light emitter 8 is accommodated in the rotary head 7. The light emitter 8 comprises a laser diode 9, a collimating lens 10, a rod lens 11, etc. A laser beam 13 emitted from the laser diode 9 is projected as linear luminous fluxes extending in a vertical direction.
The upper portion of the rotation mechanism accommodating unit 3 is protruding upward from the housing 1. A gap between the housing 1 and the rotation mechanism accommodating unit 3 is sealed by a bellows 14, and the protruding portion of the rotation mechanism accommodating unit 3 and the rotary head 7 are enclosed by a cover 15. The cover 15 has a light projection window 16, and the laser beam 13 is projected through the light projection window 16.
When the laser diode 9 is turned on and the motor 5 is rotated, the rotary head 7 is rotated via the rotation shaft 4 so that the laser beam 13 is rotated in a horizontal direction.
A labyrinthine seal 17 serving as a waterproof means is provided between the rotary head 7 and the rotation mechanism accommodating unit 3, and a gap between the rotary head 7 and the rotation mechanism accommodating unit 3 is sealed by the labyrinthine seal 17.
Now, referring to FIG. 7, description will be given on the labyrinthine seal 17.
On the upper surface of the rotation mechanism accommodating unit 3, annular projected rims (ridges) 18 and annular grooves 19, each having cross-sectional profile in rectangular shape, are disposed concentrically and in double arrangement respectively. On the lower surface of the rotary head 7, annular grooves 21 and annular ridges 22 are arranged concentrically. The annular ridge 18 is movably engaged in the annular groove 21, and the annular groove 19 is movably engaged with the annular ridge 22. The annular ridge 18 and the annular groove 21 as well as the annular groove 19 and the annular ridge 22 are not in contact with each other. A narrow space 23 with cross-sectional profile in crank-like shape is formed in the radial direction.
Because the bending space 23 with crank-like shape is formed between the rotation mechanism accommodating unit 3 and the rotary head 7, the intrusion of water, dust, etc. from outside to the inner space of the rotation mechanism accommodating unit 3 can be prevented. The rotary head 7 can be rotated without any resistance because the rotating portion is not contact with the fixed portion in the labyrinthine seal 17.
It is preferable that the space 23 is small for the purpose of preventing direct intrusion of rainwater on rainy day or under windy and rainy weather or the like. If the space 23 is small, capillary phenomenon occurs. In such case, gradual intrusion of water from outside cannot be prevented.
Therefore, by the conventional type water preventive means, perfect waterproof effect cannot be necessarily obtained when the surveying instrument is used under severe rainy condition or under rainy weather for long time.